Heating Ventilation Air-conditioning and Refrigeration (HVAC & R) systems typically include a heat exchanger unit, e.g., an outdoor unit, having a fan arranged to draw air over a heat exchanger. After being drawn over the heat exchanger coil, the air is moved by the fan through a fan ring, where the air is generally exhausted to the atmosphere. The fan ring provides a path through which air may leave the heat exchanger unit. The fan ring typically includes a geometry that provides diffusion of the air in order to reduce the amount of power required by the fan.
A conventional fan ring with a bell-mouth shape results in undesirable recirculation of the air within the heat exchanger unit and more turbulent airflow profiles. The recirculation of the air undesirably concentrates the flow of air in certain portions of the heat exchanger coil and prevents adequate airflow in other portions of the heat exchanger coil. The portions the heat exchanger that do not receive adequate airflow exchange less heat and reduce the efficiency of the heat exchanger unit. In addition, the turbulent airflow profile undesirably results in a large amount of noise being produced by the heat exchanger unit.
Fan rings, such as the fan ring described in U.S. Pat. No. 5,615,999 to Sukup, hereafter referred to as Sukup, which is herein incorporated by reference in its entirety, have been used as air flow management systems for use in conjunction with fans. Sukup describes a vane axial fan housing having an inlet end and an outlet end. The inlet end has an inlet opening circumscribed by an adjacent venturi-shaped flange integrally formed in the inlet endplate. The venturi shape of the flange extends away from the inlet end and toward the outlet end. A drawback to the cross-sectional shapes, such as the one shown in Sukup, is that the airflow through the unit is not uniform and recirculation near the inlet end of the fan housing prevents efficient flow of air through the fan housing. In addition, the fan and the flow of air through the fan ring results in a large amount of noise.
What is needed is a fan ring structure that provides a substantially uniform airflow across the heat exchanger coil of a heat exchanger unit to provide increased efficiency, while decreasing the amount of noise generated by the fan and the air flowing through the fan ring.